Mind and Body

Staying Alert: Maintaining Coffee Consumption

Regular coffee drinkers appear to need caffeine to return to their normal state of alertness, say researchers.

This runs counter to popular belief that drinking caffeinated beverages offers some added boost in alertness.

"Although caffeine consumers feel alerted by caffeine, the effect is actually only bringing you back from caffeine withdrawal-induced, low-level alertness," says study author Peter Rogers, at the University of Bristol in England. "You are not gaining anything over and above a non-consumer of caffeine."

Caffeine, sometimes called the most commonly used drug in the world, acts on the central nervous system's receptors for the neurotransmitter adenosine, according to information in the report. Adenosine is involved in regulating blood pressure, as well as sleepiness and wakefulness, alertness, and anxiety responses.

Heavy Coffee Drinkers Need the Daily Dose

In the study reported in the medical journal Neuropsychopharmacology, researchers asked 379 participants to abstain from drinking caffeinated beverages for 16 hours. They then gave half of the participants 100 milligrams of caffeine (the equivalent of one to two cups of coffee), and another 150 milligrams of caffeine an hour and a half later. The other half received a placebo (non-active substance).

Participants also were asked about their normal consumption of caffeinated beverages. Light caffeine consumers were those who drank less than the amount of caffeine found in one cup of coffee. A cup of coffee’s total caffeine is dependent on brand and brewing method, among other factors, says Rogers.

While both light caffeine drinkers and heavier caffeine drinkers reported feeling more alert after being given caffeine, there were marked differences in the responses to the placebo.

Those who normally drank few caffeinated beverages did not notice much of a difference in their level of alertness when given a placebo versus caffeine. Heavier caffeine drinkers given the placebo, however, reported a sharp drop-off in feelings of alertness.

In addition, heavier caffeine consumers given placebo were also much more likely to report having a headache.

"What this study does is provide very strong evidence for the idea that we don't gain a benefit in alertness from consuming caffeine," explains Rogers. "Although we feel alert, that's just caffeine bringing us back to our normal state of alertness."

Furthermore, abstaining from caffeine when you are used to having it can cause a "caffeine hangover," he notes. "The nice thing about a caffeine hangover is you can get rid of it quickly by drinking coffee.”

Caffeine Anxiety Buzz Enjoyed by Some

Researchers also looked at caffeine-induced anxiety, a common side effect that is more pronounced in people with a variation in a certain gene, the ADORA2A gene.

In this study, about 20 percent of participants had this gene variation. Other research has put the number of people in the general population with the variant as high as one-third.

Researchers found people with the anxiety-producing variant tended to drink a bit more coffee, suggesting that the "anxiety buzz" caused by caffeine is not necessarily unpleasant, says Rogers.

"They don't seem to particularly mind it, in fact, they might like that anxiety buzz," he says.

Participants who typically consumed caffeinated beverages also seemed to develop a tolerance to its anxiety-producing effects. Among regular caffeine drinkers, there was little difference in feelings of anxiety whether they had been given a placebo or the real thing, while light caffeine drinkers reported significantly more anxiety after being given caffeine.

Dr. Peter Martin, at Vanderbilt University in Nashville, Tenn., says the study is an interesting look at the biological effects of caffeine. However, not everyone who drinks a lot of caffeinated beverages experiences withdrawal such as headaches when they cut back or quit.

And compared to other "drugs," the effects of caffeine are mild, and coffee and tea in particular may have other health benefits.

"No one is going to change what they do, and there's no reason to change,” says Dr. Martin. “There is a lot of data to suggest caffeine improves motor performance and memory performance."

Always consult your physician for more information.

August 2010

More about Caffeine

A stimulant, caffeine affects the nervous system minutes after you drink it. Positive effects include better reaction time, mental acuity, alertness, and mood, as well as pain relief.

But caffeine may also cause nervous jitters, trouble sleeping, stomach upset, and heartburn. If you stop using caffeine, you could get withdrawal symptoms.

According to the American Heart Association (AHA), caffeine stimulates the central nervous system, releases free fatty acids from adipose (fatty) tissue, and affects the kidneys, increasing urination, which can lead to dehydration.

Besides coffee, caffeine is found in tea, chocolate, cocoa, and colas. It is also added to certain medications, including pain relievers and cold remedies.

The amount of caffeine in two to four cups of coffee per day is not generally considered to be harmful.

Some people are more sensitive to the effects of caffeine than others. They should limit their use of caffeine. So should pregnant and nursing women.

Certain drugs and supplements may interact with caffeine. Check with your physician or other healthcare provider if you have concerns about caffeine's effects on you.

Whether high caffeine intake increases the risk of coronary heart disease is still under study, according to the AHA. Many studies have been done to see if there is a direct link between caffeine, coffee drinking, and coronary heart disease with conflicting results. This may be due to the way the studies were done and confounding dietary factors. However, moderate coffee drinking (1-2 cups per day) does not seem to be harmful.

People who routinely drink coffee or other caffeinated beverages can experience "caffeine withdrawal" 12–24 hours after the last dose of caffeine. This withdrawal generally resolves within 1-2 days. A headache is the most typical symptom of caffeine withdrawal, but anxiety, fatigue, drowsiness, and/or depression may also be experienced.

Always consult your physician for more information.

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